1. Field of the Invention
The present invention relates to a data processing apparatus and a data processing method.
2. Description of the Related Art
As a conventional method of encryption and decryption of data, Advanced Encryption Standard (AES), specified by Federal Information Processing Standard (FIPS) 197 (National Institute of Standards and Technology (NIST), issued in 2001), is known.
Further, as a method to improve security in AES, White-Box Cryptography is known (Non-Patent Document 1, Non-Patent Document 2 and the like, for example).
Further, a White-Box Cryptography system with input dependent encodings is known. Specifically, the system includes a network of a plurality of basic blocks arranged for collectively performing a cryptographic operation. An encoder is arranged for encoding output data of a first one of the plurality of basic blocks into an encoder-output according to a selected one of a plurality of encoding schemes, the selection depending on an input-message to the system. A compensator is arranged for recoding intermediate data to compensate for the effect of the encoding according to a selected one of a plurality of recoding schemes. Using variable encodings instead of fixed encodings complicates reverse engineering the white-box cryptographic system. (Patent Document 1 or the like, for example).
However, according to the conventional methods, data may be decrypted if a method is used such as analyzing the data based on a relationship between input and output in AES, and the data is not sufficiently made difficult to be decrypted.